1. Field of the Invention
Embodiments of the present invention generally relate to methods and apparatus for manufacturing an expandable tubular. Particularly, the present invention relates to methods and apparatus for manufacturing a corrugated expandable tubular. Embodiments of the present invention also relate to methods and apparatus for expanding an expandable tubular.
2. Description of the Related Art
In the oil and gas exploration and production industry, boreholes are drilled through rock formations to gain access to hydrocarbon-bearing formations, to allow the hydrocarbons to be recovered to surface. During drilling of a typical borehole, which may be several thousand feet in length, many different rock formations are encountered.
Rock formations having problematic physical characteristics, such as high permeability, may be encountered during the drilling operation. These formations may cause various problems such as allowing unwanted water or gases to enter the borehole; crossflow between high and low pressure zones; and fluid communication between a highly permeable formation and adjacent formations. In instances where a sub-normal or over-pressured formation is sealed off, the permeability of the formation may be such that high pressure fluids permeate upwardly or downwardly, thereby re-entering the borehole at a different location.
Damage to rock formations during drilling of a borehole may also cause problems for the drilling operation. Damage to the formation may be caused by the pressurized drilling fluid used in the drilling operation. In these situations, drilling fluid may be lost into the formation. Loss of drilling fluid may cause the drilling operation to be halted in order to take remedial action to stabilize the rock formation. Loss of drilling fluid is undesirable because drilling fluids are typically expensive. In many cases, drilling fluids are re-circulated and cleaned for use in subsequent drilling procedures in order to save costs. Therefore, loss of high quantities of drilling fluid is unacceptable.
One method of overcoming these problems involves lining the borehole with a casing. This generally requires suspending the casing from the wellhead and cementing the casing in place, thereby sealing off and isolating the damaged formation. However, running and cementing additional casing strings is a time-consuming and expensive operation.
Furthermore, due to the installation of the casing, the borehole drilled below the casing has a smaller diameter than the sections above it. As the borehole continues to be extended and casing strings added, the inner diameter of the borehole continues to decrease. Because drilling operations are carefully planned, problematic formations unexpectedly encountered may cause the inner diameter of the borehole to be overly restricted when additional casing strings are installed. Although this may be accounted for during planning, it is generally undesired and several such occurrences may cause a reduction in final bore diameter, thereby affecting the future production of hydrocarbons from the well.
More recently, expandable tubular technology has been developed to install casing strings without significantly decreasing the inner diameter of the wellbore. Generally, expandable technology enables a smaller diameter tubular to pass through a larger diameter tubular, and thereafter be expanded to a larger diameter. In this respect, expandable technology permits the formation of a tubular string having a substantially constant inner diameter, otherwise known as a monobore. Accordingly, monobore wells have a substantially uniform through-bore from the surface casing to the production zones.
A monobore well features each progressive borehole section being cased without a reduction of casing size. The monobore well offers the advantage of being able to start with a much smaller surface casing but still end up with a desired size of production casing. Further, the monobore well provides a more economical and efficient way of completing a well. Because top-hole sizes are reduced, less drilling fluid is required and fewer cuttings are created for cleanup and disposal. Also, a smaller surface casing size simplifies the wellhead design as well as the blow out protectors and risers. Additionally, running expandable liners instead of long casing strings will result in valuable time savings.
There are certain disadvantages associated with expandable tubular technology. One disadvantage relates to the elastic limits of a tubular. For many tubulars, expansion past about 22-25% of their original diameter may cause the tubular to fracture due to stress. However, securing the liner in the borehole by expansion alone generally requires an increase in diameter of over 25%. Therefore, the cementation operation must be employed to fill in the annular area between the expanded tubular and the borehole.
One attempt to increase expandability of a tubular is using corrugated tubulars. It is known to use tubulars which have a long corrugated portion. After reforming the corrugated portion, a fixed diameter expander tool is used to insure a minimum inner diameter after expansion. However, due the long length of corrugation and the unevenness of the reformation, a problem arises with the stability of the expander tool during expansion. For example, the reformed tubular may be expanded using a roller expander tool. During expansion, only one roller is typically in contact with the tubular as the expander tool is rotated. As a result, the expander tool may wobble during expansion, thereby resulting in poor expansion of the tubular.
There is, therefore, a need for a method and an apparatus for manufacturing a tubular which may be expanded sufficiently to line a wellbore. There is also a need for a method and apparatus for expanding the diameter of a tubular sufficiently to line a wellbore. There is a further need for methods and apparatus for stabilizing the expander tool during expansion. There is a further need for methods and apparatus for expanding the reformed tubular using a compliant expander tool.